The invention relates to compositions comprising a linear low density copolymer of ethylene and an alpha-olefin containing 4 to 10 carbon atoms (LLDPE), and to films of improved properties formed from such compositions.
Linear low density polyethylene is ethylene copolymerized with alpha olefins of 3 to 10 carbon atoms. Improvements in impact resistance of films of linear low density polyethylene (hereinafter xe2x80x9cLLDPExe2x80x9d) are desirable. Normal LLDPE resins lacks the melt strength required to blow films under high stalk extrusion conditions, often used to blow HMW-HDPE, which result in excellent film impact properties. One recent exception is a DMAC [xe2x80x9dDMAC being an acronym for dimethylaluminum chloride] cocatalyzed LLDPE resins. A high molecular weight component of the DMAC cocatalyzed LLDPE resins is accompanied by an increased melt strength required to be blown into film under high stalk conditions used in HDPE film production.
In the present invention, the melt strength of LLDPE is increased by treatment with low levels of peroxides. Low levels of crosslinking of the LLDPE results with low levels of peroxides. This allows the LLDPE to be blown into film under high stalk conditions. The treated LLDPE can be fabricated with improved processability into blown films having improved impact properties. The impact strengths of these LLDPE films is significantly higher than that of films from uncrosslinked LLDPE films blown under non-stalk conditions.